Today, many electronic devices and systems require a form of user authentication. For example, in a payment system, a smart card may be used to initiate a payment and to authenticate a user. In addition to conventional user authentication via a personal identification number (PIN), a smart card may also include a fingerprint sensor for capturing the user's fingerprint. In that case, the captured fingerprint may be used to ascertain that the smart card is presented to a terminal by its rightful owner, for example. However, it is difficult to determine whether a captured fingerprint belongs to a living person. The same may apply to other devices, such as mobile phones or tablets, which are used for transactions and use fingerprint-based user authentication.